------- Comment #13 from rguenther at suse dot de 2009-02-05 10:31 -------
Subject: Re: [4.3/4.4 Regression] -fprofile-generate
= huge SCCs for PRE
On Thu, 5 Feb 2009, bonzini at gnu dot org wrote:
>
>
> ------- Comment #12 from bonzini at gnu dot org 2009-02-05 10:26 -------
> FRE is not a problem because all the time (93%) is spent computing ANTIC; of
> this, half is phi_translate and the other half is bitmap_set operations.
>
> I get a relatively good (15%) improvement from
>
> Index: tree-ssa-sccvn.c
> ===================================================================
> --- tree-ssa-sccvn.c (revision 143938)
> +++ tree-ssa-sccvn.c (working copy)
> @@ -398,9 +398,14 @@ vn_reference_op_eq (const void *p1, cons
> static hashval_t
> vn_reference_op_compute_hash (const vn_reference_op_t vro1)
> {
> - return iterative_hash_expr (vro1->op0, vro1->opcode)
> - + iterative_hash_expr (vro1->op1, vro1->opcode)
> - + iterative_hash_expr (vro1->op2, vro1->opcode);
> + hashval_t result = 0;
> + if (vro1->op0)
> + result += iterative_hash_expr (vro1->op0, vro1->opcode);
> + if (vro1->op1)
> + result += iterative_hash_expr (vro1->op1, vro1->opcode);
> + if (vro1->op2)
> + result += iterative_hash_expr (vro1->op2, vro1->opcode);
> + return result;
> }
>
> /* Return the hashcode for a given reference operation P1. */
>
>
> and another 8% from this:
>
> Index: tree-ssa-pre.c
> ===================================================================
> --- tree-ssa-pre.c (revision 143938)
> +++ tree-ssa-pre.c (working copy)
> @@ -216,11 +216,11 @@ pre_expr_hash (const void *p1)
> case CONSTANT:
> return vn_hash_constant_with_type (PRE_EXPR_CONSTANT (e));
> case NAME:
> - return iterative_hash_expr (PRE_EXPR_NAME (e), 0);
> + return iterative_hash_hashval_t (SSA_NAME_VERSION (PRE_EXPR_NAME (e)),
> 0);
> case NARY:
> - return vn_nary_op_compute_hash (PRE_EXPR_NARY (e));
> + return PRE_EXPR_NARY (e)->hashcode;
> case REFERENCE:
> - return vn_reference_compute_hash (PRE_EXPR_REFERENCE (e));
> + return PRE_EXPR_REFERENCE (e)->hashcode;
> default:
> abort ();
> }
>
> (Tested with "make check RUNTESTFLAGS=tree-ssa.exp=*[pf]re*"). At least these
> two kick hashing almost out of the profile and bring PRE down from 50% to 40%
> of the compilation time. They also speedup a bit the bitmap_sets since
> get_or_alloc_expression_id was also doing hashing.
>
> The remaining main offenders are phi_translate_set and phi_translate_1. Apart
> from some bitmap_sets, their profile is quite flat so no more
> microoptimization
> I guess.
>
> I'll bootstrap/regtest the above.
Ah, can you test in addition to the above
--- ../trunk/gcc/tree-ssa-sccvn.c 2009-01-28 13:11:34.000000000
+0100
+++ gcc/tree-ssa-sccvn.c 2009-02-01 12:26:36.000000000 +0100
@@ -316,6 +316,10 @@
const struct vn_constant_s *vc1 = (const struct vn_constant_s *) p1;
const struct vn_constant_s *vc2 = (const struct vn_constant_s *) p2;
+ /* Early out if this is not a hash collision. */
+ if (vc1->hashcode != vc2->hashcode)
+ return false;
+
return vn_constant_eq_with_type (vc1->constant, vc2->constant);
}
and similar in the other hash compare fns?
Richard.
>
>
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35639
